Synchronized clutch with thrust bar



Filed Dec. 11, 1948 April 27, 1954 fnuenl of fl ehnez M (Zr-manifold g wM 0% chronizer ring against the Patented Apr. 27, 1954 2,676,684SYNCHRONIZED CLUTCH WITH THRUST BAR Kenneth M. Armantrout,

to Borg-Warner Corp corporation of Illinois Application December 11,1948, Serial No. 64,820

1 Claim. 1

This invention relates to transmissions and more particularly to thrustbars for use in synchromesh type transmissions and to methods for makingthe same.

Thrust bars, or shifter plates, are widely employed in certain types ofsynchromesh transmissions and where so used generally perform twofunctions. The thrust bars, upon being urged forward by the slidingcollar of the shift mechanism, which is in turn moved by the shiftinglever, push the synchronizer or blocker ring forward into frictionalengagement with the cooperating surface of the gear to be synchronizedand at the same time, by entering into suitable slots formed in thering, connect the ring in driving relationship to the drive shaft,thereby causing the ring to rotate in synchronism with the drive shaft.In performing the first of these two functions, the thrust bar carriesthe entire axial pressure occasioned in pressing the syncooperatingsurface of the gear to be synchronized and accordingly the end of thethrust bar is subjected to considerable longitudinal stress. This stresstends to bend the end of the thrust bar backward. In practice, it hasbeen found that unless the end of the thrust bar is made particularlyresistant to this bending action, the end portion may be flexedsufiiciently over a period of use to be actually broken off.Furthermore, in performing the second function, the end of the thrustbar, as it engages the side of the slot in the synchronizer ring, issubjected to a shearing stress exerted at right angles to the bendingstress, thus increasing the tendency to deformation and possibleultimate breakage. It readily will be apparent to those skilled in theart that deformation or breakage of a thrust bar is a serious problemand particularly so because of the relative inaccessibility of thethrust bars when the transmission has been assembled and placed in use.

Since the development of this type of synchromesh transmission, numerousefiorts have been made to provide thrust bars which will stand up inservice and not be deformed or' otherwise necessitate replacement;United States Patent No. 2,221,900, issued November 19, 1940 to White eta1., exemplifies some of these efforts and discloses various forms ofthrust bars that have met with some success. This patent discloses ingeneral three forms of thrust'bars: Fig. 3 shows a thrust bar comprisinga solid block of metal. This form is relatively diflicult to manufactureand undesirably heavy. A second form Muncie, Ind, assignor oration,Chicago, 111., a

is illustrated in Fig. 6 of this patent and comprises an elongatedrectangular primary plate having the requisite surface configuration andhavin the two ends thereof bent downwardly at right angles. This plateis reinforced by a second plate wedged between the ends of the primaryplate. This second form is obviously a more complicated structure thanwould ordinarily be desired and unless the primary and secondary platesare rigidly secured together as by welding, there is considerable dangerof the plates being pulled apart. A third form of thrust bar is thatillustrated in Fig. 8 and comprises a stamping in which the end and sidemembers are bent downwardly from a rectangular top portion to form agenerally box-like structure, the side members tending to provide somelongitudinal support for the end members by virtue of their location.However, substantially no improvement is obtained in resistance to theshearing stress to which the end members are subjected in service.

An object of the present invention is to provide a new and improvedthrust bar and a simple and efficient method or" making the same.

A further object of the present invention is to provide a thrust bar ofeconomical design which will have improved resistance to bothlongitudinal and shearing stresses.

In accordance with one embodiment of this invention, a thrust bar ofsubstantially box-like configuration may be formed in a combined drawingand bending operation from a substantially rectangular blank of sheetmetal having tabs at either end. In the forming operation, the sides ofthe box-shaped thrust bar are drawn so that all four sides are integralwith the top portion of the bar and also integrally joined with eachother to form in effect a continuous rim about the periphery of the topportion, the rim extending downwardly therefrom. At the same time, dueto the bending of the tabs, the tabs are moved to occupy a position fromtheir original position in the blank and to extend beyond the lower edgeof the side portions of the rim.

Other objects and advantages of the present invention will be apparentfrom the following detailed description taken in conjunction with thedrawings wherein:

Fig. l is a plan view of a blank from which a thrust bar may be formedin accordance with this invention;

Fig. 2 is an enlarged, fragmentary, transverse, sectional view of 'acombined drawing and bend- 3 ing die which may be employed in accordancewith one embodiment of this invention;

Fig. 3 is a View similar to Fig. 2 showing the position of the diemembers and the shape of the thrust bar at the completion of the drawingmove ment of the die;

Fig. 4 is a sectional view taken along the line 1- of Fig. 3; and

Fig. is an axial sectional view of a transmission synchronizer embodyingthe invention.

Referring first to Fig. 5 of the drawing there is shown therein asynchronizing transmission including a pair of alignedtorque-transmitting members and 3 I, the forward end of the member 3!being piloted, as at in the rear end of the member 36. The member 3a maybe the driving shaft of a conventional automobile trans mission, and themember 3i the driven shaft of such a transmission. A hub at is securedto the shaft 3! as by means of a splined connection 36, and is locatedagainst axial movement by a retaining ring 3i, on one side, and areduction geared torque-transmitting member as on the other side, thelatter being mounted against a shoulder 33 formed on the shaft 3|.

The reduction geared member 38 is driven from the drive shaft iiithrough constant mesh gearing includinga gear 39 formed on the driveshaft 30, a countershaft All having a gear ii meshing with the gear 39,and having a second gear 42-, and a gear 43 formed on thetorquetransmitting member '33 and meshing with the gear 42.

A positive drive connection is adapted to be established between thetorque-transmitting members so and Si, or between the reduction gearedtorque-transmitting member 3t and the member 3! by an axially movablejaw clutch element formed with internal clutch teeth 41, in slidingsplined engagement with teeth 48 forming the periphery of the hub member34, and adapted to be shifted axially by a shifting fork A l to bringthe teeth E? into positive clutching engagement with clutch teeth isformed on the torque transmitting member 3%, or clutch teeth '46 formedon the torque-transmitting member 38.

Upon being moved into clutching engagement with the teeth it, themovable clutch element 35 will receive rotation from the drive shaft 3tand transmit it directly through the hub to the driven shaft 3i. Uponbeing moved in the opposite direction into clutching engagement with theteeth the movable clutch element 35 will receive rotation from thetorque-trans" mitting member as through the countershaft 4c, and willtransmit such rotation through the hub member 34 to the driven shaft 3I.

i In order to synchronize either torque-transmitting member 30 or 33with the movable jaw clutch element 35, preparatory to establishing suchpositive clutch engagement, there is provided a pair of synchronizerrings 49, each including a substantially cylindrical collar portion 59rotatably mounted within the rim portion of the hub 34, and a peripheralportion which is provided with blocker teeth iii between which the teeth41 of the movable jaw clutch element must pass before the clutchingengagement with the teeth 45 or 46 may be established. The opposed endsof the teeth 4"! and 5! may be chamfered, in accordance with well knownpractice. The synchronizer rings 49 are provided with internal conicalfriction clutch faces adapted to engage complementary external conicalfriction clutch element 35 clutch faces of friction clutch elements 52and respectively, formed on the torque-transmitting members 30 and 38,.

The mounting of the synchronizer rings i?) within the rim of the hub 3is such as to allow them to move both circumferentially and axially withrespect to the hub. The axial movement enables them to establishengagement with their respective cooperating friction clutch elements 52and 53. Such axial movement is transmitted to a synchronizer ring fromthe movable jaw during the initial stage of shifting movement thereof,through the medium of a thrust bar or a plurality of thrust bars M,which are interposed between the movable jaw clutch sleeve 35 and thehub iii, and received in notches 55 in the periphery of the hub 3 Thethrust bars E i are confined against circumferential movement by thenotches 55, but are free to slide longitudinally therein in pathsparallel to the axis of the torque-transmitting members 3i: and 3 I.

The ends of the thrust bars W- are received in notches 56 in thesynchronizer rings at, and are abutted against the rings it so as totransmit axial thrust thereto.

The notches 56 are wider than the ends of the bars 5 3 so as to allow alimited amount of circumferential shifting movement of the synchronizerrings relative to the hub, whereby a synchronized ring may shift from aposition in which the blocker teeth 5| are effective to block axialshifting movement of the movable jaw clutch sleeve 35, to a position inwhich the movable jaw clutch sleeve 35 may pass on into clutchin;engagement with a jaw clutch element =15 or it. By thus utilizing theprojecting ends of the thrust bars for engagement in notches in thesynchronizer rings, we eliminate the necessity of employing separateconnecting means for establishing a lost motion connection between thesynchronizer rings as and the hub 25%. However it is to be understoodthat other forms of lost motion connection, well known the art, may beemployed.

In the preferred form of the invention, the transmission of axial thrustfrom the movable jaw clutch element '35 to the thrust bars 5% providedfor in the form of a break-away con nection comprising a projection 5?formed in tegrally in the central region of a thrust bar, and acorresponding recess 53 in a tooth or teeth i: of the movable jaw clutchsleeve which recess E8 the projection El is engageable.

The thrust bars at are yieldingly urged radially outwardly by a pair ofresilient expander 5c. The rings 59 are received between the web portionof the hub 3t, and the opposed extremities of the collar portions iii!of the synchroni rings ie. They are formed with a normal diametergreater than the diameter of the inner sides of the assembled thrustbars iii... so that when assembled, they are biased under compression soas to urge the bars radially outwardly into engagement with the interiorof the movable jaw clutch sleeve '35.-

The manner whereby the thrust bars may be made and the detailsofconfiguration thereof will now be described.

Referring now to Fig. 1 wherein a slant which may be formed from a sheetmetal is illustrated, it will be noted that the blank comprises anelongated, substantially, rectangular body portion ll having at eitherend thereof a tab i2 comprising essentially an extension of the bodyportion but being of somewhat narrower width. Such a blank may bereadily punched from a strip, or partially punched from a strip and thencarried in the strip to the next step, as for example in a continuouspunching and drawing apparatus.

In the combined drawing and bending operation of this invention, theblank I9 is positioned in a die press shown fragmentarily in Figs. 2, 3,and i. The die press comprises cooperating lower and upper die membersI3 and I4 of rectangular cross section, the die members I3 and I 4 beingslidably journaled insuitable apertures I5 and I6, respectively, formedin a stripper plate I? and upper die block IS. The lower die member I3is made sufficientlysmaller in cross section than the aperture I6 formedin the die block It to provide the drawing action as the die member orram I3 is moved upwardly to bring the blank into engagement with the diemember I 4 and block I8.

The entrance to the aperture I6 is beveled as indicated at I9 both tofacilitate the initial drawing action and also to provide the bendingaction which causes the tabs l2 to be bent at right angles to the bodyportion II of the blank It as the ram It is moved upwardly. Upwardmovement of the ram I 3 compresses the peripheral area along the sidesof the blank I I and adjacent the tabs I2, drawing the metal in thisarea to form the sides and ends of the thrust bar. By virtue of thedrawing action the ends of the thrust bar 25 form a continuous band orflange extending downwardly at right angles from the rectangularperiphery of the central portion of the blank Ill, thus providing anopen ended substantially box-like structure. The tabs I2 extend somewhatbeyond the lower edge of the structure but in the same plane therewithas clearly indicated in Fig. 4.

The lower die member I3 has a boss 28 of elongated transverse crosssection formed in the center of its upper surface and this bosscooperates with a slightly larger recess 2| of similar configurationformed in the lower end of the upper die member I 4 to form the hump orprojection indicated at 57 on the completed thrust bar in Figs. 3 and 4.The boss 2!) and cooperating recess 2| are preferably shaped so that thehump will have a prolate, hemispheroidal surface configuration, beinggenerally elliptical in cross section and having its long dimensiondisposed at right angles to the long dimension of the thrust bar 54. Itwill be understood that this hump 51, in cooperation with the recess orannular groove 58 formed on the interior of the sliding collar 35 of thetransmission shifting mechanism causes the thrust bar 54 to moveinitially with the sliding collar 35, the

hump 5? being urged into the groove 58 by the rings 59 which bearagainst the underside of the thrust bar 54 and are retained in positionthereagainst by the tabs I 2. Because the hump 51 is only resilientlypressed against the sides of the annular groove 58, increased pressureon the shift lever is causes the sliding collar 35 to break away fromthe thrust bar 54 to establish the posi-, tive clutch engagement. Theparticular surface configuration of the thrust bar hump 51 in accordancewith this invention is not only simple to form in the same drawingoperation wherein the sides of the thrust bar 54 are formed, but also isespecially suited for the breakaway action required.

By correctly proportioning the die members and associated elements andlimiting their upward travel, it will be evident that it is feasible, inaccordance with the present invention, to restrict the drawing action sothat while the tabs I2 are moved to occupy in the thrust bar 55 aposition substantially from their original position in the blank, thetabs actually are subjected to no drawing action. On the other hand, itis possible also, in accordance with the present invention, to both bendthe tabs in the manner stated, and also to draw the tabs to increase forexample the amount of projection. Finally, it is also possible, inaccordance With the present invention, to form the tabs completely inthe drawing operation from a simple rectangular block. Such drawingnecessarily reduces the thickness of the end portions of the thrust barand thereby the inherent strength and, consequently, where the tabs arealso formed in the drawing operation ordinarily the blank must be madeof somewhat thicker material than otherwise or of material which isthicker adjacent the ends of the blank.

It is to be noted that the drawing operation lends itself particularlywell to the forming of rounded edges and corners. Such rounded edges andcorners are generally desired in order to facilitate entry of the thrustbars into the slots 56 formed in the synchronizer rings 9. Thus thismethod avoids the usually necessary additional step of chamfering theends of the thrust bar, since this is readily accomplished in thedrawing operation. Furthermore, while drawing tends to reduce thethickness of the metal, at the same time like forging, because itincreases the density of the metal by compression, it increases the unitstrength, thus compensating for the decrease in thickness.

From the foregoing it will be evident that the thrust bar in accordancewith this invention combines the best features of previous designs whileavoiding their disadvantages. By joining the sides and ends as acontinuous rim, the sides and ends reinforce each other in the areas ofcritical stress and it has been found in practice that this design ofthrust bar is durable and highly resistant to deformation or breakage.At the same time this design is readily manufactured in accordance withthe method of this invention in a simple and economical manner.

What is claimed is:

In a transmission synchronizer, three coaxial torque transmittingmembers, a pair of synchronizer elements respectively drivinglyassociated with one of said members, each of said synchronizer elementsbeing shiftable axially for respectively establishing a frictionaldriving connection between said one member and the other two of saidmembers, a jaw clutch sleeve encircling said one member and drivinglyconnected thereto and shiftable axially in opposite directions forrespectively establishing a positive driving connection between said onemember and either of said other two members, said one member includingmeans defining a plurality of axially extending slots and saidsynchronizer elements each including means defining an equal number ofnotches,'and a plurality of thrust bars respectively disposed in saidslots in said one member, each of said thrust bars comprising a hollowbox-like structure having a substantially rectangular cross portion andsides depending therefrom and bent at substantially right anglesthereto, the sides of each of said thrust bars being integral with thecross portion thereof and being integral with each other so that saidsides form an integral continuous band extending about the periphery ofthe cross portion, a pair of said depending sides on each of said thrustbars being opposed to each other and being formed with tabs thereonrespectively adapted to be received in the slots in said synchronizerelements, and each of said thrust bars having a hump formedsubstantially in the center of its cross portion which hump is adaptedto yieldingly engage said jaw clutch sleeve such that upon axialshifting movement of said sleeve axial thrust therefrom is transmittedthrough the humps to the thrust bars and thence toone of thesynchronizer elements through one of the opposed pair of depending sideson each of said thrust bars .for establishing the frictional driving 8connection between said one member and one of said other two members.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,682,348 Porter Aug. 28, 1928 1,974,981 Carvahlo Sept. 25,1934 2,067,459 Noll et a1 Jan. 12, 1937 2,179,568 White NOV. 14, 19392,201,149 Best May 21, 1940 2,221,893 White Nov. 19, 1940 2,221,900White et a1 Nov. 19, 1940 2,221,901 Barr Nov. 19, 1940 2,312,749 BullockMar. 2, 1943 2,459,561 Yawman Jan. '18, 1949

